The present invention relates generally to a control method and an apparatus to detect the presence of a first object and monitor a relative position of the first object, or subsequently placed objects. The invention relates more specifically to a control method and apparatus to detect the presence of a container within a dispensing station and automatically controlling a fill level of dispensed product into the container until the container is considered full.
Aside from making the dispenser control fully automatic, a main consideration in the development of the present invention is to provide an automatic dispensing control which can compete economically with prior art lever actuated dispensing valves and manually operated push-button electric switch valve controls. To be commercially successful in this market, a dispensing valve control must demonstrate not only the automatic characteristics of detecting the presence and absence of a container and activating or deactivating a dispenser in response thereto, but also provide reliable fill control with limited operator interface.
One common method of automatic dispensing for soft drinks in the prior art is based on time portion control. An example of such a method is disclosed in U.S. Pat. No. 4,890,774 that shows a valve having multiple push buttons corresponding to different sized containers, such as small, medium, large, etc. When one of these buttons is depressed, a beverage is dispensed for a predetermined time period assigned to that individual size. The primary disadvantage of such a system is that differences in ice portions can cause the container to be either over or under-filled. In application, these controls may have a "top off" button to fill the container in the event a user does not place enough ice in the container. Where such differences in ice portions cause the container to be under-filled by the timer, the "top off" button is depressed which causes the dispenser to activate for a short predetermined time. However, when under-filled by only a small amount, the "top off" cycle may actually overfill the container. Conversely, if too much ice is first placed in the container, the predetermined dispense time will initially overfill the container. An overfill not only results in waste of dispensed product, but also excess operator time for cleaning each overfilled container. Such systems may also experience fill level problems due to variations in flow rates, which are common in soft drink dispensing machines due to variations in liquid line pressure. Further, when an operator mistakenly pushes a button relating to a container larger than the container to be filled, the control will overflow the container by an amount of product equal to the difference in container sizes resulting in even more waste. These programmable timers also require reprogramming the dispensing times each time the establishment changes the container sizes. Another limitation of these controls is that they are labor intensive in that they require the operator to consistently place the correct amount of ice in the container for that particular container size, and any variation in the ice will require the operator to spend additional time at the dispensing machine to depress the "top off" button, and since the "top off" cycle is so short, the operator will usually stand there and wait for the end of the cycle. Such a system inevitably results in inconsistent fill levels which can create customer dissatisfaction and/or wasted product. Timed portion control units have been used in non-self serve applications for many years despite the many shortcomings because to date, it has been considered the best overall system.
Another such system is disclosed in U.S. Pat. No. 4,202,287 which shows a fluid dispensing control system sensing a container size with a set of photosensor and associated light sources that activate a timer in the control system for dispensing fluid for a pre-determined time dependent on the container size detected. However, this system continues to dispense until a timing cycle is completed regardless of whether or not the cup is still present under the dispensing valve. Also, the amount of fluid dispensed is dependent upon preset container sizes. That is, if an establishment changes the size of its medium size cup, the preset amount of fluid dispensed for a medium size cup must be changed or else the cup will not be filled or will be overfilled. This is particularly problematic when the diameter of a container is changed because such a change is usually overlooked but results in volume change that affects fill level.
Other methods of automatic dispensing are described in U.S. Pat. Nos. 4,559,979, 4,798,232, 4,817,689 and 4,890,651, and 5,036,892. Such systems employ ultrasonic transducers located adjacent the dispensing spigot to sense the location of a container and/or the product level in the container. When a container is located underneath the spigot, the control is designed to dispense product into the container. The transducer monitors the liquid level and halts the flow of the beverage when the container is sufficiently filled. One disadvantage of this system is the high cost of the control and transducer. Another shortcoming is the control's limited ability to recognize foam. It has been observed that the response rate of the ultrasonic sensor is generally not fast enough to accurately track the changing foam level and therefore, causes the foam to spill over before the dispenser is deactivated. In the one such patent, ultrasonic energy is used for sensing the machine grate, the cup lip, the top of any ice in the cup, and the rising liquid level, and thereafter generates signals corresponding to the travel time of the ultrasonic energy to a control module. In order to accomplish this, changes are made to the gain for various distance measurements. Further, dip switches are used for setting the ice level. If it is determined that the actual ice height in a container is greater than that allowed by the dip switch settings, an over-ice indicator flashes and the cup detection routine begins again. The system will not activate the dispenser unless the actual ice height is less than the amount selected by the dip switches. The use of ultrasonic components and extensive software and hardware results in a system that is relatively expensive. The application for this technology in the market place has been limited due to these limitations.
Another method of automatic dispensing is described in U.S. Pat. No. 4,972,883. In such a system, the container base is positioned at an angle with respect to the dispenser and the container is placed against a long lever to dispense product. The lever is connected to an electrical switch and when the container is pushed against the lever, the switch closes and activates a solenoid to dispense beverage. Beverage flow is halted when the container is removed from the lever or when a product spills over the lip of the container and liquid is sensed on the lever. One disadvantage of this system is that it is not a true contact-free dispensing system because the container must contact the lever in order to vend the product. Another disadvantage of this system is that when a container is not physically removed, the dispenser is not deactivated until the beverage spills over the side, thus causing both the container and the lever arm to become sticky with syrup and causing waste of product.
It would be advantageous to have a method and apparatus capable of detecting a container position under a dispenser and capable of monitoring a fill level after dispenser activation to accurately fill a container regardless of the ice content, the container size, independent of operator interface, monitor the continued presence of the container, and at a cost effective end cost.